﻿namespace SenenFernandez.SmartExtensionMethods.Converter
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Globalization;
    using System.Linq;
    using System.Windows.Data;

    /// <summary>
    /// Enum Converter class.
    /// </summary>
    public class EnumConverter : IValueConverter
    {
        private readonly Dictionary<Type, List<object>> cache = new Dictionary<Type, List<object>>();

        /// <summary>
        /// Converts a value. 
        /// </summary>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        /// <param name="value">The value produced by the binding source.</param>
        /// <param name="targetType">The type of the binding target property.</param>
        /// <param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
        {
            object result = Binding.DoNothing;
            if (value != null)
            {
                var type = value.GetType();
                if (!cache.ContainsKey(type))
                {
                    var fields = type.GetFields().Where(field => field.IsLiteral);
                    var values = new List<object>();
                    foreach (var field in fields)
                    {
                        var attribute = (DescriptionAttribute[]) field.GetCustomAttributes(typeof (DescriptionAttribute), false);
                        values.Add(attribute.Length > 0 ? attribute[0].Description : field.GetValue(value));
                    }
                    cache[type] = values;
                }
                result = cache[type];
            }
            return result;
        }

        /// <summary>
        /// Converts a value. 
        /// </summary>
        /// <returns>
        /// A converted value. If the method returns null, the valid null value is used.
        /// </returns>
        /// <param name="value">The value that is produced by the binding target.</param>
        /// <param name="targetType">The type to convert to.</param><param name="parameter">The converter parameter to use.</param>
        /// <param name="culture">The culture to use in the converter.</param>
        public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
        {
            return Binding.DoNothing;
        }
    }
}